A.1 B.2 C.4 D.8
A.Sn22++OH-==SnO32-+H2O+2e B.Cr2O72++14H++3e==2Cr3++7H2O C.Bi2O5+10H++2e===Bi3++5H2O D.H3AsO3+6H++6e===AsH3+3H2O
A.1,4,1,8,1,1 B.1,2,2,3,4,2 C.1,4,1,8,1,8 D.2,8,2,16,2,8